The present invention relates to a connection system for connecting a pipe carrying a hot fluid to a plastic member containing or carrying a fluid at a substantially lower temperature. It also relates to the use of such a system in an internal combustion engine.
In numerous industrial applications it is necessary to inject a hot fluid into a fluid at a substantially lower temperature carried by a plastic member. Such a situation poses a problem as regards the temperature stability of the plastic member at the place where the pipe carrying the hot fluid is connected thereto.
A problem of this type is especially encountered in the design of internal combustion engines enabling the quantity of polluting exhaust gases emitted to be reduced. From this standpoint, one solution consists, in fact, in subjecting part of the exhaust gases to recirculation in the combustion chamber or chambers in the engine, thereby making it possible to complete their combustion and thus to reduce the quantity of pollutants emitted.
In order to implement this solution, it is necessary to equip the engine with a pipe which takes part of the exhaust gases back towards the inlet manifold. Given the high temperature of the exhaust gases, usually of the order of several hundred degrees, a metal pipe (generally designated by "EGR pipe"--Exhaust Gas Recirculation) is often used for this purpose. On the other hand, the inlet manifolds of combustion engines are not subjected to high temperatures and are more and more frequently made of plastic.
However, it is clear that problems arise when it is desired to connect an EGR pipe, heated to several hundred degrees, to a plastic member. Part of the solution to this problem, known already, consists in making the connection via a metal bell, through which the pipe passes, acting as a heat shield between the EGR pipe in which the hot gases flow and the wall of the plastic manifold, at the place where the pipe penetrates into the manifold.
However, it is necessary to connect, firmly and in a sealed manner, the EGR pipe to the inlet manifold.
A known connection system consists in fixing the abovementioned bell, via threaded metal inserts embedded in the wall thickness of the manifold, by screws passing through lateral eyelets fixed to the bell or forming part thereof. However, this system constitutes a solution of little advantage. The reason for this is that it comprises numerous components, several operations (and as many screws) are involved in (un) fitting it, and it requires the use of a tool. The presence of metal inserts within the manifold furthermore complicates its manufacture and its subsequent possible recycling.
The connection system chosen must consequently comply with many requirements. Thus, it must, especially, ensure sealing, even at high temperatures, and preferably must be simple to (un)fit, that is to say requiring no special tool nor the application of a large force. In order for it to be usable in particular on small engines, it should furthermore take up little room. It is also advantageous for it to be able to be applied to cylindrical pipes and also to pipes of different cross-sections.
Generally, it is also desired to be able to connect the pipe to the plastic member without having to rotate it, this rotation being likely to be difficult to achieve because the other end of the pipe is rigidly fixed, or because of an elbow or elbows which the pipe may comprise. Finally, it is desirable that the system chosen be composed of few components, so as to simplify its implementation and to reduce its cost.
The same requirements are generally imposed in industrial applications other than that of exhaust gas recirculation in internal combustion engines.